There are many circumstances in which it is desirable to be able to inspect areas of a hot furnace. For example, when determining whether a furnace needs repair by ceramic welding techniques (such as is described in U.S. Pat. No. 5,378,493, the disclosure of which is incorporated by reference herein) or in determining whether a repair has properly been made, especially for difficult to access portions of the furnace, it is difficult to get an accurate determination of existing conditions. In most conventional furnace camera systems, because of the adverse conditions inside the furnace the camera remains on the outside of the furnace and a water-cooled lens tube is inserted into the furnace which communicates with the camera. The water-cooled lens tube is typically short in length and straight, and can only view objects which are in the direct line of site of the end of the lens tube. This not only restricts the areas of the furnace that can be viewed, but can distort the view. The 5,378,493 patent incorporated by reference herein positions a CCD camera near, but necessarily spaced from, the end of a lance that is used for applying the ceramic welding composition, and the camera is cooled by the lance's water jacket, and a curtain of air may be passed over the camera's lens to keep it clear of particles and to facilitate cooling thereof. However, because of the positioning of the camera on the lance an accurate view of all portions of the furnace is still not provided, nor is the camera as interactive with the operator as desired.
According to the present invention, a video camera system is provided, as well as a method of inspecting a furnace while at high temperature using the camera, which allow virtually any portion of the furnace to be accurately viewed, and which can easily provide the operator with real time feedback so as to facilitate a wide variety of operations within the furnace. The system according to the invention is simple, with a minimum number of components, yet with optimized utility, and is useful in association with furnaces of almost any practical temperature range, including over 2000.degree. F., in fact to temperatures approaching 3000.degree. F.
The shutter speed of the camera provided according to the invention may be readily--in fact substantially instantly--varied. This allows the camera to stop "blinding" of the signal (i.e. too much light) and allows use in areas where there are substantial quantities of UV, visible, and IR light. The speed of the shutter can vary from 1/60 per second to 1/10,000 per second, and can be controlled manually through a CCU and a monitor or video headset.
According to one aspect of the present invention a monitoring system for a furnace is provided comprising the following components: A fluid cooled lance having a first end adapted to be held by an operator, and a second end adapted to be inserted into the furnace. A camera (e.g. microcamera, endoscope, or boroscope, typically with a lateral sight angle of about 30.degree.) is mounted in the lance at the second end thereof, and cooled along with the lance, and including a camera lens. An electrical connection to the camera mounted within the lance, and extending exteriorly of the furnace. And a control unit (e.g. in a portable casing, e.g. having a total weight of about 20 pounds or less) mounted exteriorly of the furnace, and connected to the electrical connection. The portable casing is desirably airtight and/or watertight.
The camera is preferably in a waterproof metal casing (to protect the camera from condensation) with the electrical cord extending outwardly from the casing substantially opposite the lens, and the camera lens is preferably protected from radiant heat by a second heat resistant but substantially distortion free (e.g. sapphire) lens. The electrical cord is covered at least adjacent the casing with an aramid (e.g. kevlar)-reinforced covering material. Air cooling passages are also preferably provided which are connected up to air under pressure (e.g. at least about 30 psi, e.g. standard about 65 psi compressed air) to further cool the camera.
The system further comprises a substantially stationary video monitor in the control unit operatively connected to the camera, and preferably includes headgear for the operator of the lance. A portable real time video monitor is mechanically mounted on the headgear so that it may be seen by the operator, and the video monitor is operatively connected to the camera through the control unit. A video controller may also be mounted in the control unit. For simplicity, a single electrical power source is connected to the control unit for powering all of the components of the system.
The lance is cooled by a water jacket including an inlet and an outlet both disposed adjacent the first end of the lance, and the water jacket substantially surrounds the entire periphery of the camera. The lance water jacket and the camera are constructed and positioned so that the camera may operate at a temperature of over 2000.degree. F. in the furnace, and allow ready inspection of virtually all portions of the furnace in an accurate manner.
According to another aspect of the present invention a monitoring system for a furnace is provided comprising the following components: A fluid cooled lance having a first end adapted to be held by an operator, and a second end adapted to be inserted into the furnace. A camera mounted in the lance adjacent the second end thereof, and cooled along with the lance, and including a camera lens. An electrical connection to the camera mounted within the lance, and extending exteriorly of the furnace. A control unit mounted exteriorly of the furnace, and connected to the electrical connection. Headgear for the operator of the lance. And a portable real time video monitor mechanically mounted on the headgear so that it may be seen by the operator, and operatively connected to the camera through the control unit. The details of the system may be as described above.
According to another aspect of the present invention a method of inspecting a furnace while a temperature of over 400.degree. F. (e.g. over 2000.degree. F., up to about 3000.degree. F.) using a video camera mounted in a free end of the lance, is provided. The method comprises: [a] inserting the lance free end into the furnace while at a temperature of over 400 degrees F. (e.g. over 2000.degree. F.), and moving the lance free end around within the furnace; [b] cooling the camera by circulating cooling fluid in a cooling fluid jacket around the camera; and [c] outside of the furnace, viewing an area of the furnace in the field of view of the camera in a substantially undistorted manner on a substantially real time basis.
[a] is typically practiced by a human operator wearing headgear, and [c] is then preferably practiced viewing a real time video monitor mounted on his or her headgear. The method further comprises viewing an area of the furnace in the field of view of the camera on a substantially real time basis that is substantially stationary (during use) in location (such as a video monitor in a control unit), and recording the viewed images from the camera at the substantially stationary location (e.g. with a conventional video recorded mounted in the same control unit). The method may further comprise providing a single power source to the system, including powering the camera and any other electrical components or structures associated with it. [b] is preferably practiced by substantially continuously circulating liquid in a water jacket, and also preferably directing compressed air (e.g. at least about 30 psi) past the camera's metal casing to further cool it. If the method is practiced through a relatively low temperature furnace cooling may be done by circulating gas (such as air) rather than a liquid, or a liquid and gas.
It is the primary object of the present invention to provide a simple yet effective system and. method for inspecting virtually all areas of the furnace while at high temperature, in a simple and effective manner. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.